Diatom of the month – March 2016: Mastogloia calcarea

by Luca Marazzi*

‘Who’ is it and where does it live?
This diatom is a symmetric biraphid species, i.e. it has a raphe on either valve allowing it to move sliding on substrata. Mastogloia calcarea was ‘discovered’ / described by Sylvia Lee during her PhD research at Evelyn Gaiser’s lab at FIU; it is similar to M. smithii and M. lacustris, common freshwater species in this predominantly marine genus. This new species typically lives in karstic wetlands of the Caribbean region (Mexico, Jamaica and Belize) and in the Florida Everglades, as compared to the temperate zones where M. smithii and M. lacustris live and are found1.

 Mastogloia calcarea in valve (top) and girdle (bottom) view (http://westerndiatoms.colorado.edu/)1; scalebar = 10 µm.

                                            Original drawing of Mastogloia smithii labeled 341 and 341 β (source: Smith 1856)2.

Why are we studying it?
Describing new species is obviously not just a hobby performed by detail-loving biologists, but an essential way to discover which organisms are where and why, given their size, shape, intra- and extra-cellular features, motility or lack thereof, and so on. Taxonomic investigations lead to the peer-reviewed establishment of new genera, species, varieties via gradual time-consuming steps. Slate & Stevenson (2007)3 and Gaiser et al. (2010)4, prepared the ground for the discovery of two new diatom species in the Everglades by highlighting different morphology and ecology of two types of Mastogloia. In the end, Sylvia Lee described M. pseudosmithii alongside M. calcarea during her PhD with Evelyn Gaiser. The former differs in morphology and ecology from this month’s diatom, that instead prefers brackish (slightly salty) waters with higher phosphorus - coming from seawater - and lower pH (due to higher peat accumulation)1; whereas M. calcarea, a structural engineer and keystone species (like cyanobacteria)3, is best adapted to the lower phosphorus and higher pH conditions of the cohesive mats located in the inland Everglades.

What can you do?
As we have learned, there are diatoms loving the freshwater they find in sawgrass-dominated areas of the Everglades, and those preferring brackish waters towards the ecological interface (ecotone) where the mangroves are creeping-in. With sea levels undoubtedly rising before our (either worried or indifferent) eyes, saltwater is invading our (beloved or too-swampy-and-mosquito-ridden-to-go-to) wetland’s freshwater areas from a higher level, creating what FIU’s SERC director Todd Crowl called ‘a pressure problem’ in a recent TED talk. So here is what every (soon to be or already) concerned citizen or visitor can do: explore the Everglades tomorrow or next week or next month -alone, with your partner and/or kids! You can do it on foot, by canoe or kayak, by airboat and overnight - you can even go on a full moon bike ride in Shark River Valley!

Abundant periphyton mats likely containing this diatom, where the mangroves meet the sawgrass in lower Shark River Slough (Photo by Stephen Davis – 26 June 2014).        

This will help you understand why we study plants, animals, and even tiny glassed-celled algae called diatoms: they are our witnesses of the fast rise of sea level that is transforming marshes into brackish water ponds, and will flood large parts of Miami and South Florida sooner than we thought. And there is no time to waste to find the solutions to cut the heat-trapping gas emissions that warm the planet, and thus thermally expand the oceans’ volume and further increase sea level by glaciers’ and icesheets’ melting. Everyone can do their small part, for example following simple steps to cut our carbon footprint; these choices / actions can, like a drop in the ocean, slow down climatic changes and create a new more sustainable world, for real!

* Postdoctoral Associate in Dr. Evelyn Gaiser's lab at Florida International University.

1. Lee S.S., Gaiser E.E., Van de vijver B., Edlund M.B. & Spaulding S.A. 2014. Morphology and typification of Mastogloia smithii and M. lacustris, with descriptions of two new species from the Florida Everglades and the Caribbean region. Diatom Research 29: 325– 350.
2. Smith W. 1856. Synopsis of the British Diatomaceae. Volume 2. J. Van Voorst, London. 107 pp.
    marsh. Diatom Research 22: 355–386.
4. Gaiser E.E., La Hée J.M., Tobias F.A.C. & Wachnicka A.H. 2010. Mastogloia smithii var. lacustris Grun.: A
    Sciences of Philadelphia 160: 99–112.


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